1. Field of the Invention
The invention relates to an automobile-detecting apparatus, particularly to an asynchronous photography automobile-detecting apparatus.
2. Description of the Prior Art
In the conventional technology, a binocular cameras system installed on a same horizontal plane is used to carry on the distance measurement of stereovision, in order to form the image at the same time. There is a fixed distance between the binocular cameras, thus there is a disparity between left image and right image. This disparity is the coordinate difference of left image and right image at X-axis. The distance between object and lens can be obtained from the disparity (such as ΔP) to obtain the goal of precise distance measurement.
The images taken by the conventional synchronous binocular cameras system are formed on a same horizontal line, no matter the object and the synchronous binocular cameras system are under static state, or the object and the synchronous binocular cameras system are under dynamic state. It is to say that the pixels of the object will drop on the same Y-axis of left image and right image. When the pixels of the object drop on the same Y-axis of left and right images, it will be beneficial for searching and comparing step. It not only can raise the processing speed, but also can increase the success rate of searching.
However, the synchronous binocular cameras system needs special extra hardware circuit and design, in order to trigger the exposure control of binocular cameras at the same time. It not only will increase the volume of camera, but also will raise the cost of cameras. Furthermore, the corresponding image retrieving device is required for the image retrieval at host computer end, which will increase the volume of equipment.
In addition, when the asynchronous binocular cameras system is used for vehicle detection, a difference value on the Y-axis of left image and right image (such as ΔY) will be generated due to the difference of exposure time and the vibration of vehicle body. It will cause the difficulty of comparison. Moreover, the respective exposure of asynchronous binocular cameras will cause different illumination and gray level between the left image and right image, due to the difference of shutter speed and aperture size during the exposure time.
As for the acquisition of disparity ΔP, the left image and right image are searched totally to find out the difference at X-axis conventionally. Assume Sw denotes the width of searching scope and the left image and right image of synchronous binocular cameras lie at the same level, then the searching scope will be Sw×1. As for the asynchronous binocular cameras system, ΔY has to be considered, thus the searching scope will be Sw×2×ΔY.
Thus, in the conventional synchronous photography technique, there are drawbacks of too large volume and high cost, and the asynchronous photography technique is not completely suitable for current vehicle detection technique. In order to meet the demand of vehicle detection, the relevant photography techniques have to be developed to save the cost of manpower and time etc., and the image of vehicle can be detected correctly.